Air carrier Captain reported departing the gate before receiving the required DG documents. The documentation was eventually received and confirmation was sent to dispatch prior to departure.

Narrative

We received a planned dangerous goods form during ACARS initialization. Which was done almost an hour prior to push back. We completed all our preflight procedures and the aircraft was loaded with Passengers and Cargo. All doors were closed and ramp reported ready for push back. At that point we had forgotten about the Dangerous Goods. After push back we started engines and were ready for taxi; but was going to be a short taxi and we still did not have final weights. ATC moved us to a remote area to be out of the way. We contacted Dispatch; Station ops; and load planning to get final weights. We finally got them after about 10-15 minutes of waiting. The Dangerous Good (DG) form came off the printer and we were both aware we had to send a message on ACARS when it was printed before even reading it. I told the First Officer (FO) it had the instructions on the form on what message to send and where in the ACARS. After readying the form I realized this needed to be done before push back; but it was too late. I sent the confirmation code via ACARS. We loaded the final weights and did the before takeoff checklist and continued without incident.