Air carrier Captain reported a return to the gate due to missing required Dangerous Goods documents during departure taxi. After further review it was determined that DG documents were not required due to the type of DG.

Narrative

Upon pushback we did not receive final weights. We taxied to runway and sent the 'late weights' prompt. After no response and approximately 20 minutes we made it to the front of the line for departure and had to tell Tower we needed more time for weights. They brought us onto the runway and around the backside to wait. Operations and Load Planning said they hadn't received the numbers from the ramp crew and were struggling to get into contact with them. After another 5 minutes; Operations told us; 'the ramp crew is unsure if they strapped down the dangerous goods' so we need to return to gate. This raised a red flag for my FO and I because we had no DG (Dangerous Goods) summary. We returned to the gate and I contacted the Dispatcher to get a patch with the Load Planner to figure out what was happening. The Load Planner contacted the DG department and eventually figured out that the type of item we were carrying did not require a DG summary to be sent to the pilots. We then pushed back again and departed.