Tanak headed to the final service of the gravel event with a slightly reduced 51.6-second lead over Hyundai’s Teemu Suninen.
Suninen came under pressure from charging Hyundai team-mate Thierry Neuville (+58.3s), who won the morning’s two stages.
Toyota’s Elfyn Evans completed the loop in fourth overall (+1m19.1s) ahead of title rival Kalle Rovanpera (+2m07.8s), with the third Toyota driven by Takamoto Katsuta in sixth (+4m42.4s).
Sunday began with a fast yet technical pass through stage 13, held in overcast conditions.
Rally leader Tanak could afford to opt for a measured approach having built up lead of more than a minute.
He successfully navigated the test without issue, albeit 10.8s slower than the pacesetter Neuville, as his overall lead was trimmed to 52.3s.
Keen to overhaul team-mate Suninen to claim second overall, the Belgian took the stage win by 4.8s from his Hyundai stablemate to reduce the gap to 9.1s.
"I had a good stage, I enjoyed it," said Neuville. "A couple of small moments, I was on the limit on many corners but the car was working nice so I enjoyed the ride."
Evans’ hopes of stealing third were dealt a blow as he couldn’t match Neuville’s speed and dropped 5s. Title rival Rovanpera, celebrating his 23rd birthday, remained in fifth overall after clocking the fifth-fastest stage time.
There was, however, drama for M-Sport Rally1 debutant Gregoire Munster before the stage began as he was involved in a road traffic accident that left his Puma with minor damage.
"Just before the refuelling out of the service we had a road accident with a car, so we were a bit scared with the right side," said Munster.
Stage 14 (El Ponen), a dress rehearsal for the rally-ending Power Stage, followed and it was again claimed by Neuville. The Hyundai driver beat team-mate Suninen by 2.4s, leaving only 6.7s separating the pair heading into the final loop.
Tanak was third-fastest with Evans and Rovanpera completing the top five stage times.
In WRC2, Toksport Skoda driver Oliver Solberg maintained his lead over team-mate Gus Greensmith to hold seventh and eighth positions overall.
