diff --git a/subsys/bluetooth/controller/ll_sw/nordic/lll/lll_adv_iso.c b/subsys/bluetooth/controller/ll_sw/nordic/lll/lll_adv_iso.c
index 40aeaa211db89c..91ca0b1d0c6372 100644
--- a/subsys/bluetooth/controller/ll_sw/nordic/lll/lll_adv_iso.c
+++ b/subsys/bluetooth/controller/ll_sw/nordic/lll/lll_adv_iso.c
@@ -625,26 +625,36 @@ static void isr_tx_common(void *param,
 
 	/* Get ISO data PDU, not control subevent */
 	if (!pdu) {
-		uint8_t payload_index;
+		uint16_t payload_index;
 
 		if (lll->ptc_curr) {
-			uint8_t ptx_idx = lll->ptc_curr - 1;
+			/* FIXME: Do not remember why ptc is 4 bits, it should be 5 bits as ptc is a
+			 *        running buffer offset related to nse.
+			 *        Fix ptc and ptc_curr definitions, until then there is an assertion
+			 *        check when ptc is calculated in ptc_calc function.
+			 */
+			uint8_t ptx_idx = lll->ptc_curr - 1U; /* max. nse 5 bits */
 			uint8_t ptx_payload_idx;
-			uint32_t ptx_group_mult;
+			uint16_t ptx_group_mult;
 			uint8_t ptx_group_idx;
 
 			/* Calculate group index and multiplier for deriving
 			 * pre-transmission payload index.
 			 */
-			ptx_group_idx = ptx_idx / lll->bn;
-			ptx_payload_idx = ptx_idx - ptx_group_idx * lll->bn;
-			ptx_group_mult = (ptx_group_idx + 1) * lll->pto;
-			payload_index = ptx_payload_idx + ptx_group_mult * lll->bn;
+			ptx_group_idx = ptx_idx / lll->bn; /* 5 bits */
+			ptx_payload_idx = ptx_idx - ptx_group_idx * lll->bn; /* 8 bits */
+			ptx_group_mult = (ptx_group_idx + 1U) * lll->pto; /* 9 bits */
+			payload_index = ptx_payload_idx + ptx_group_mult * lll->bn; /* 13 bits */
+
+			/* FIXME: memq_peek_n function does not support indices > UINT8_MAX,
+			 *        add assertion check to honor this limitation.
+			 */
+			LL_ASSERT(payload_index <= UINT8_MAX);
 		} else {
-			payload_index  = lll->bn_curr - 1U;
+			payload_index  = lll->bn_curr - 1U; /* 3 bits */
 		}
 
-		payload_count = lll->payload_count - lll->bn + payload_index;
+		payload_count = lll->payload_count + payload_index - lll->bn;
 
 #if !TEST_WITH_DUMMY_PDU
 		struct lll_adv_iso_stream *stream;
diff --git a/subsys/bluetooth/controller/ll_sw/nordic/lll/lll_sync_iso.c b/subsys/bluetooth/controller/ll_sw/nordic/lll/lll_sync_iso.c
index b3af4fd8404e98..c17370dcf0b008 100644
--- a/subsys/bluetooth/controller/ll_sw/nordic/lll/lll_sync_iso.c
+++ b/subsys/bluetooth/controller/ll_sw/nordic/lll/lll_sync_iso.c
@@ -52,6 +52,7 @@ static void isr_rx_estab(void *param);
 static void isr_rx(void *param);
 static void isr_rx_done(void *param);
 static void isr_done(void *param);
+static uint16_t payload_index_get(const struct lll_sync_iso *lll);
 static void next_chan_calc(struct lll_sync_iso *lll, uint16_t event_counter,
 			   uint16_t data_chan_id);
 static void isr_rx_iso_data_valid(const struct lll_sync_iso *const lll,
@@ -659,8 +660,7 @@ static void isr_rx(void *param)
 		 * Ensure we are not having offset values over 255 in payload_count_max, used to
 		 * allocate the buffers.
 		 */
-		payload_offset = (lll->latency_event * lll->bn) +  (lll->bn_curr - 1U) +
-				 (lll->ptc_curr * lll->pto);
+		payload_offset = (lll->latency_event * lll->bn) + payload_index_get(lll);
 		if (payload_offset >= lll->payload_count_max) {
 			goto isr_rx_done;
 		}
@@ -1031,8 +1031,7 @@ static void isr_rx(void *param)
 		if (bis) {
 			struct node_rx_pdu *node_rx;
 
-			payload_count += (lll->bn_curr - 1U) +
-					 (lll->ptc_curr * lll->pto);
+			payload_count += payload_index_get(lll);
 
 			/* By design, there shall always be one free node rx
 			 * available for setting up radio for new PDU reception.
@@ -1336,6 +1335,35 @@ static void isr_done(void *param)
 	}
 }
 
+static uint16_t payload_index_get(const struct lll_sync_iso *lll)
+{
+	uint16_t payload_index;
+
+	if (lll->ptc_curr) {
+		/* FIXME: Do not remember why ptc is 4 bits, it should be 5 bits as ptc is a
+		 *        running buffer offset related to nse.
+		 *        Fix ptc and ptc_curr definitions, until then there is an assertion
+		 *        check when ptc is calculated in ptc_calc function.
+		 */
+		uint8_t ptx_idx = lll->ptc_curr - 1U; /* max. nse 5 bits */
+		uint8_t ptx_payload_idx;
+		uint16_t ptx_group_mult;
+		uint8_t ptx_group_idx;
+
+		/* Calculate group index and multiplier for deriving
+		 * pre-transmission payload index.
+		 */
+		ptx_group_idx = ptx_idx / lll->bn; /* 5 bits */
+		ptx_payload_idx = ptx_idx - ptx_group_idx * lll->bn; /* 8 bits */
+		ptx_group_mult = (ptx_group_idx + 1U) * lll->pto; /* 9 bits */
+		payload_index = ptx_payload_idx + ptx_group_mult * lll->bn; /* 13 bits */
+	} else {
+		payload_index  = lll->bn_curr - 1U; /* 3 bits */
+	}
+
+	return payload_index;
+}
+
 static void next_chan_calc(struct lll_sync_iso *lll, uint16_t event_counter,
 			   uint16_t data_chan_id)
 {
@@ -1377,8 +1405,7 @@ static void isr_rx_iso_data_valid(const struct lll_sync_iso *const lll,
 	node_rx->hdr.handle = handle;
 
 	iso_meta = &node_rx->rx_iso_meta;
-	iso_meta->payload_number = lll->payload_count + (lll->bn_curr - 1U) +
-				   (lll->ptc_curr * lll->pto);
+	iso_meta->payload_number = lll->payload_count + payload_index_get(lll);
 	/* Decrement BN as payload_count was pre-incremented */
 	iso_meta->payload_number -= lll->bn;
 
diff --git a/subsys/bluetooth/controller/ll_sw/ull_adv_iso.c b/subsys/bluetooth/controller/ll_sw/ull_adv_iso.c
index d1428c422b6bb1..d041f1e2a30bd5 100644
--- a/subsys/bluetooth/controller/ll_sw/ull_adv_iso.c
+++ b/subsys/bluetooth/controller/ll_sw/ull_adv_iso.c
@@ -212,7 +212,7 @@ static uint8_t big_create(uint8_t big_handle, uint8_t adv_handle, uint8_t num_bi
 				return BT_HCI_ERR_INVALID_PARAM;
 			}
 
-			if (!IN_RANGE(pto, 0x00, 0x0F)) {
+			if (pto > 0x0F) {
 				return BT_HCI_ERR_INVALID_PARAM;
 			}
 
@@ -1211,6 +1211,12 @@ static uint8_t ptc_calc(const struct lll_adv_iso *lll, uint32_t event_spacing,
 			ptc = MIN(ptc, (lll->bn * BT_CTLR_ADV_ISO_PTO_GROUP_COUNT));
 		}
 
+		/* FIXME: Do not remember why ptc is 4 bits, it should be 5 bits as ptc is a
+		 *        running buffer offset related to nse. Fix ptc and ptc_curr definitions,
+		 *        until then lets have an assert check here.
+		 */
+		LL_ASSERT(ptc <= BIT_MASK(4));
+
 		return ptc;
 	}
 
diff --git a/subsys/bluetooth/controller/ll_sw/ull_sync_iso.c b/subsys/bluetooth/controller/ll_sw/ull_sync_iso.c
index 94933a0178c3e4..f9aa64863cfa14 100644
--- a/subsys/bluetooth/controller/ll_sw/ull_sync_iso.c
+++ b/subsys/bluetooth/controller/ll_sw/ull_sync_iso.c
@@ -494,6 +494,13 @@ void ull_sync_iso_setup(struct ll_sync_iso_set *sync_iso,
 		}
 
 		lll->ptc = lll->nse - nse;
+
+		/* FIXME: Do not remember why ptc is 4 bits, it should be 5 bits as ptc is a
+		 *        running buffer offset related to nse.
+		 *        Fix ptc and ptc_curr definitions, until then we keep an assertion check
+		 *        here.
+		 */
+		LL_ASSERT(lll->ptc <= BIT_MASK(4));
 	} else {
 		lll->ptc = 0U;
 	}